Bump elliptic and ethers in /scripts/cast-on-tenderly

Removes [elliptic](https://github.com/indutny/elliptic). It's no longer used after updating ancestor dependency [ethers](https://github.com/ethers-io/ethers.js). These dependencies need to be updated together.


Removes `elliptic`

Updates `ethers` from 5.7.2 to 6.13.2
- [Release notes](https://github.com/ethers-io/ethers.js/releases)
- [Changelog](https://github.com/ethers-io/ethers.js/blob/main/CHANGELOG.md)
- [Commits](ethers-io/ethers.js@v5.7.2...v6.13.2)

---
updated-dependencies:
- dependency-name: elliptic
  dependency-type: indirect
- dependency-name: ethers
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>